It is probably a non-issue but one downside is that if people realize that you are doing this they can just pick a new "user" and reach you even if you have blocked their original address.

It would be interesting to do something like this with signatures. You could generate new addresses "on the fly" by picking a prefix and signing it. Then you can use this email and it can't be modified in a way to generate a new valid email.

For example you could have walmart-oaiua83n@yourdomain.example and they couldn't just change it to goodcompany@example.com.